Combine potatoes, sugar, 1/2 cup melted butter, rind, juice, cinnamon, and nutmeg; beat at medium speed of an electric mixer until smooth. Spoon mixture into a lightly greased 1- quart casserole.
Combine pecans and coconut; sprinkle over top of sweet potato mixture. Dot with 1 tablespoon butter. Bake at 350° for 20 minutes or until topping is lightly browned.